Electrum

Electrum is a naturally occurring alloy of gold and silver, with trace amounts of copper and other metals. It is found in rivers. 

The ancient Greeks called it "gold" or "white gold", as opposed to "refined gold". Its color ranges from pale to bright yellow, depending on the proportions of gold and silver. It has been produced artificially, and is also known as "green gold".Emsley, John (2003) Nature's building blocks: an A–Z guide to the elements. Oxford University Press. . p. 168

Electrum has been used for coins.

 References 

Category:Ores
Category:Gold alloys
Category:Silver alloys
Category:Native element minerals